Bioscience Methods 2024, Vol.15, No.6, 264-274 http://bioscipublisher.com/index.php/bm 269 6.2 Targeted editing of key genes In sweet potato, key genes involved in starch biosynthesis, such as IbGBSSI (granule-bound starch synthase I) and IbSBEII (starch branching enzyme II), have been targeted using CRISPR/Cas9 to directly regulate starch synthesis pathways. For instance, CRISPR/Cas9-mediated knockout of IbGBSSI and IbSBEII in sweet potato cultivars resulted in significant alterations in amylose content, demonstrating the potential of this technology to modify starch quality (Wang et al., 2019). Such targeted editing allows for the precise manipulation of metabolic pathways, thereby improving both the yield and nutritional quality of sweet potatoes (Andersson et al., 2018; Wang et al., 2019; Li et al., 2021). 6.3 Challenges and successes in gene editing Despite the promising applications of CRISPR/Cas9 in sweet potato breeding, several technical challenges remain. One major challenge is the efficient delivery of the CRISPR/Cas9 components into sweet potato cells, which are often recalcitrant to transformation (Andersson et al., 2018; Tussipkan and Manabayeva, 2021). Additionally, the polyploid nature of sweet potato complicates the editing process, as multiple alleles of a gene must be simultaneously targeted to achieve the desired phenotype (Wang et al., 2015; Wang et al., 2019). However, successes have been reported, such as the high mutation efficiency (62%-92%) achieved in sweet potato cultivars, leading to significant changes in starch composition without affecting total starch content (Table 1) (Wang et al., 2019). These successes underscore the potential of CRISPR/Cas9 to revolutionize sweet potato breeding by enabling precise genetic modifications that enhance crop traits (Abdelrahman et al., 2018; Chen et al., 2019; Wang et al., 2019). Table 1 Mutation rates of CRISPR/Cas9 in sweet potato (Adopted from Wang et al., 2019) Cultivar Target gene No. of plants with Cas9 gene No. of plants with mutation Mutation rates of transgenic plants Xushu22 IbGBSSI 25 23 92.0% Xushu22 IbSBEII 47 40 85.1% Taizhong6 IbGBSSI 24 15 62.5% Taizhong6 IbSBEII 11 7 63.6% 7 Multi-Omics Approaches for Studying Yield and Starch Content in Sweet Potato 7.1 Transcriptomics Transcriptomics involves the comprehensive analysis of RNA transcripts to understand gene expression patterns. In sweet potato, transcriptomic studies have identified key genes involved in starch biosynthesis and yield improvement. For instance, the gene IbGBSSI, which encodes granule-bound starch synthase I, has been shown to play a crucial role in starch accumulation. Elevated expression of IbGBSSI during starch accumulation phases was observed, indicating its importance in enhancing starch content in sweet potato (Haque et al., 2023). Additionally, CRISPR/Cas9-mediated mutagenesis targeting starch biosynthetic genes such as IbGBSSI and IbSBEII has demonstrated the potential to modify starch quality, further emphasizing the role of transcriptomics in identifying and manipulating key genes for improved yield and starch content (Wang et al., 2019). 7.2 Metabolomics Metabolomics focuses on the comprehensive profiling of metabolites within a biological system. In sweet potato, metabolomic studies have been instrumental in elucidating the starch synthesis pathway and identifying key metabolites involved in starch accumulation. For example, the study of metabolites in the starch synthesis pathway has revealed the accumulation of specific metabolites that are crucial for starch biosynthesis. The integration of metabolomics with other omics approaches has provided insights into the regulatory mechanisms governing starch accumulation. This approach has been successfully applied in other crops, such as potato, where the simultaneous boosting of source and sink capacities led to a significant increase in tuber starch yield (Jonik et al., 2012). These findings highlight the potential of metabolomics in identifying key metabolites and regulatory mechanisms that can be targeted for improving starch content in sweet potato.
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